Coke ovens are liable to generate peeling and cracks on their surface and their wall gradually falls off due to friction between the wall and processing materials, or due to frequently repeated cooling and heating. During the conversion process of blended coals to cokes, on the other hands, tar in the blended coals is gasified. The inner wall of the coke oven that has been relatively smooth becomes so greatly roughened and its frictional resistance becomes so large due to severe temperature conditions and sedimentation of carbon particles, causing process materials and carbon particles generated by combustion to adhere on the roughened surface. Accordingly, the wall tends to develope a severely convex and concave surface and the width of the carbonization chamber is narrowed, increasing extrusion resistance of coke, causing a problem in operating the plant. Increased damage of the inner surface of the oven is an another problem.
For solving such problems, WO No. 95/31418 discloses a glaze for preventing adhesion of carbon, wherein the glaze, with a melting point of 900.degree. C. or less, basically comprises R.sub.2 O (Na.sub.2 O or K.sub.2 O) and SiO.sub.2 in which one or two of the compounds of Li.sub.2 O and B.sub.2 O.sub.3 are preferably added. This glaze contains, based on the oxide content, 10 to 40% of R.sub.2 O (Na.sub.2 O or K.sub.2 O), 10% or less of Li.sub.2 O and 10% or less of B.sub.2 O.sub.3 with a balance of SiO.sub.2. The publication describes that processors of the aforementioned components are hydroxides, carbonates, nitrates, phosphates, sulfates and chlorides.
The investigators of the present invention independently disclosed an art for surface treatment of high temperature fire resistant materials in Japanese Unexamined Patent Publication No. 8-119775, wherein fire resistance and gas permeation-preventing properties of firebricks, which are exposed to a high temperature in ovens such as ceramic ovens, cement calcination ovens and power generator boilers, are improved. In the art above, a treating material comprising 35.0 to 50.0% of sodium silicate having a molecular ratio of SiO.sub.2 /Na.sub.2 O of 3.2 to 3.8, 1.0 to 10.0% of lithium hydroxide, 1.0 to 10.0% of sodium borate, 1.0 to 10.0% of organic silicone compounds represented by a formula of R--Si(OH) (wherein R denotes an alkyl group with a carbon number of 1 to 12) and water and having a viscosity of 100 cps (20.degree. C.) or less are coated on the surface of fire bricks heated at a surface temperature of 500 to 1000.degree. C. with a spray nozzle in a thickness of 0.05 to 4.0 kg/m.sup.2 (based on the unit surface area of the fire bricks), thereby foaming a fused coating layer on the surfaces of the firebricks. When the temperature is increased thereafter, a treated layer having a high purity of SiO.sub.2 having a smooth and strong surface can be obtained by reacting the surface layers of the firebricks with the fused coating layer and by causing sodium atoms to be scattered off.